JP7390648B2 - Interconnector member and method for manufacturing interconnector member - Google Patents

Description

TECHNICAL FIELD The technology disclosed herein relates to interconnector members.

A solid oxide fuel cell (hereinafter referred to as "SOFC") is known as one type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen. A fuel cell power generation unit (hereinafter referred to as "power generation unit"), which is a constituent unit of SOFC, includes a fuel cell single cell (hereinafter referred to as "single cell") and an interconnector member. A single cell includes an electrolyte layer, and an air electrode and a fuel electrode that face each other in a predetermined direction (hereinafter referred to as "first direction") with the electrolyte layer in between. The interconnector member is electrically connected to an air electrode or a fuel electrode that constitutes a single cell.

The interconnector member includes a metal member made of a metal containing Fe and Cr (for example, ferritic stainless steel). When Cr contained in the metal member constituting the interconnector member reacts with oxygen in the air, an oxide film layer containing Cr oxide (for example, Cr ₂ O ₃ (chromia)) is formed on the surface of the metal member. Ru. Since the oxide film layer containing Cr oxide has low oxygen permeability, it suppresses oxidation of Fe, which is more undesirable for metal members. On the other hand, since the oxide film layer containing Cr oxide has high electrical resistance, if the oxide film layer grows further, the electrical resistance of the interconnector member may increase and the performance of the power generation unit may deteriorate.

In addition, when Cr contained in the metal members that make up the interconnector material evaporates and adheres to the electrodes of a single cell, a phenomenon called "Cr poisoning" occurs, which reduces the reaction rate at the electrodes. ) performance may deteriorate.

In order to suppress the performance deterioration of power generation units such as these, on the surface of the metal members constituting the interconnector member (more specifically, in contrast to the metal member in the oxide film layer disposed on the surface of the metal member) A structure in which a coating layer (hereinafter referred to as "Mn-Co coating layer") containing a spinel-type oxide containing Mn and Co (for example, MnCo ₂ O ₄ ) is formed on the side surface). is known (for example, see Patent Document 1). In the interconnector member having such a configuration, the Mn-Co film layer suppresses oxygen permeation, and therefore further growth of the oxide film layer is suppressed, resulting in an increase in the electrical resistance of the interconnector member (i.e., the unit of power generation performance deterioration) can be suppressed. In addition, in the interconnector member having such a configuration, the Mn-Co coating layer suppresses transpiration of Cr from the metal member, so occurrence of Cr poisoning of the single cell is suppressed, and as a result, the performance of the power generation unit is reduced. can be suppressed.

Japanese Patent Application Publication No. 2011-99159

In conventional interconnector members, for example, when a temperature change occurs around the interconnector member, the temperature of the Mn-Co coating layer (a coating layer containing a spinel-type oxide containing Mn and Co) changes. This causes stress due to the difference in thermal expansion between the Mn-Co coating layer and the oxide coating layer (coating layer containing Cr oxide), which may cause the Mn-Co coating layer to peel off from the oxide coating layer. be.

In addition, such issues are related to the electrolytic cell unit that is a constituent unit of a solid oxide electrolytic cell (hereinafter also referred to as "SOEC") that generates hydrogen using the electrolysis reaction of water. This is a common problem for interconnector members as well. Note that in this specification, the fuel cell power generation unit and the electrolytic cell unit are collectively referred to as an electrochemical reaction unit. Moreover, such a problem is not limited to SOFCs and SOECs, but is also common to other types of electrochemical reaction units.

This specification discloses a technique that can solve the above-mentioned problems.

The technology disclosed in this specification can be realized, for example, as the following form.

(1) The interconnector member disclosed in this specification includes a metal member containing Fe and Cr, and a first metal member containing Cr oxide, which is disposed on one side of the metal member in a first direction. An interconnector member comprising: a coating layer; and a second coating layer disposed on the one side of the first coating layer and containing a spinel-type oxide containing Mn and Co, the interconnector member comprising: The ratio of the Mn concentration (atm%) to the Co concentration (atm%) in the second coating layer is 1:1 to 2, and the one side portion of the second coating layer is the outer portion. , when a portion of the second coating layer located between the outer portion and the first coating layer is an inner portion, at least one cross section parallel to the first direction (hereinafter referred to as “ In the specific cross section), the porosity S1 (%) in the outer portion is larger than the porosity S2 (%) in the inner portion.

On the other hand, in the present interconnector member, as described above, in the specific cross section, the porosity S1 (%) in the outer part of the second coating layer is equal to the porosity S1 (%) in the inner part (of the second coating layer). The porosity is larger than the porosity S2 (%) in . Therefore, in the specific cross section, due to the presence of pores formed in the second coating layer, the thermal conductivity in the second coating layer is reduced, and as a result, the deformation (thermal expansion and heat shrinkage) is suppressed. Furthermore, due to the presence of pores formed in the second coating layer, the deformation (thermal expansion and thermal contraction) of the second coating layer is absorbed, and thereby the deformation (thermal expansion and contraction) of the second coating layer is absorbed. and heat shrinkage) are suppressed. Therefore, according to the present interconnector member, the second coating layer (the first coating layer (from) can be suppressed.

(2) In the interconnector member, the ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion of the second coating layer is 60 (atm%) or more. It may also be a configuration. In this interconnector member, since the amount of Mn present in the outer portion of the second coating layer is sufficiently larger than the amount of Co (present in the outer portion), the second coating layer The thermal conductivity in the layer is reduced and the heat transfer by electron migration in the second coating layer is reduced. Therefore, according to the present interconnector member, heat conduction in the second coating layer is suppressed, and stress is generated due to the difference in thermal expansion between the second coating layer and the first coating layer. Peeling of the second coating layer (from the first coating layer) can be more effectively suppressed.

(3) In the above interconnector member, the interconnector member includes an electrolyte layer and an air electrode and a fuel electrode that face each other in the first direction with the electrolyte layer interposed therebetween, In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction units each including an electrochemical reaction single cell in which a gas chamber facing the surface of a certain specific electrode is formed, at least one side of the electrochemical reaction cell stack is provided. A plurality of protrusions protruding from the one side are formed, the plurality of protrusions are covered with the first coating layer and the second coating layer, and the plurality of protrusions are connected to the specific electrode. a conductive member that is electrically connected to the specific electrode by and, of the second coating layer, a portion located on one side of the virtual straight line in the second direction passing through the tip of the one side of the metal member in the first direction is defined as a first portion. , the porosity Sa of the first part of the second coating layer is defined as a second part located on the other side of the virtual straight line and at least partially facing the gas chamber. The porosity may be smaller than the porosity Sb of the second portion of the second coating layer.

In this interconnector member, in the specific cross section, the porosity S1 (%) in the outer portion of the second coating layer is greater than the porosity S2 (%) in the inner portion (of the second coating layer). The large value also prevents peeling of the second coating layer (from the first coating layer) due to stress caused by the difference in thermal expansion between the second coating layer and the first coating layer. Can be suppressed. Here, in the present interconnector member, as described above, the porosity Sa of the first portion of the second coating layer is smaller than the porosity Sb of the second portion of the second coating layer. . In the second part (at least partially facing the gas chamber), due to the influence of temperature changes of the gas passing through the gas chamber, the change in the second coating layer (from the first coating layer) Peeling is likely to occur. On the other hand, since the second portion connected to the specific electrode does not face the gas chamber (excluding a small portion), the second portion of the second coating layer (the first coating layer There is no risk of peeling (from the layer). According to the present interconnector member, the porosity Sb of the second portion (at least a part of which faces the gas chamber) of the second coating layer is relatively high, so that the second Although the effect of suppressing peeling of the coating layer (from the first coating layer) is sufficiently exhibited, the porosity Sb of the second portion connected to the specific electrode is relatively small, so that the above-mentioned Current can be efficiently passed between (the convex portion of) the interconnector member and the specific electrode, and as a result, the performance of the electrochemical reaction cell stack can be improved.

(4) In the method for manufacturing an interconnector member, the steps include: a first step of preparing the metal member; a second step of forming a Mn oxide layer on the metal member by electrophoretic deposition; A third step of forming a Co-plated layer containing Co on the layer by plating, and firing the metal member that has undergone the first step, the second step, and the third step, A fourth step of forming the first coating layer and the second coating layer on the metal member may be configured. According to the present method for manufacturing an interconnector member, the ratio of the Mn concentration (atm%) to the Co concentration (atm%) in the second coating layer is 1:1 to 2, and in the specific cross section , the interconnector member is configured such that the porosity S1 (%) in the outer portion of the second coating layer is larger than the porosity S2 (%) in the inner portion of the Mn oxide layer; can do. In addition, in the method for manufacturing an interconnector member of the present invention, after forming the Mn oxide layer by electrophoretic deposition (the second step), a Co plating layer is formed in the gap created in the Mn oxide layer. (the third step), the adhesion between the second coating layer and the first coating layer becomes good, so that the adhesion of the second coating layer (from the first coating layer) Peeling is suppressed.

(5) In the method for manufacturing an interconnector member, a ketone solvent may be used as the solvent for soaking the metal member in the second step. Therefore, according to the present method for manufacturing an interconnector member, the Mn oxide layer can be formed more efficiently in the second step.

Note that the technology disclosed in this specification can be realized in various forms, for example, an interconnector member, an interconnector member and an electrochemical reaction single cell (a fuel cell single cell or an electrolytic single cell). It is realized in the form of an electrochemical reaction unit (fuel cell power generation unit or electrolytic cell unit) comprising a plurality of electrochemical reaction units, an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack) comprising a plurality of electrochemical reaction units, a manufacturing method thereof, etc. Is possible.

FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 in this embodiment. FIG. 2 is an explanatory diagram showing an XZ cross-sectional configuration of the fuel cell stack 100 at a position II-II in FIG. 1. FIG. FIG. 2 is an explanatory diagram showing a YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III in FIG. 1. FIG. 3 is an explanatory diagram showing an XZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 2. FIG. 4 is an explanatory diagram showing a YZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 3. FIG. 5 is an explanatory diagram showing the XY cross-sectional configuration of the power generation unit 102 at the position VI-VI in FIG. 4. FIG. 5 is an explanatory diagram showing the XY cross-sectional configuration of the power generation unit 102 at the position VII-VII in FIG. 4. FIG. FIG. 2 is an explanatory diagram showing a detailed configuration of an interconnector complex 200 (a portion of which an air electrode side current collector 134 is formed) in the present embodiment. FIG. 2 is an explanatory diagram showing a detailed configuration of an interconnector complex 200 (of which the air electrode side current collector 134 is not formed) in the present embodiment. It is a flowchart which shows an example of the manufacturing method of the interconnector composite body 200 in this embodiment. FIG. 2 is an explanatory diagram schematically showing a part of an example of a method for manufacturing an interconnector complex 200 according to the present embodiment. FIG. 2 is an explanatory diagram schematically showing a part of an example of a method for manufacturing an interconnector complex 200 according to the present embodiment. It is an explanatory diagram showing performance evaluation results in this embodiment.

A. Embodiment:
A-1. Configuration of fuel cell stack 100:
(Configuration of fuel cell stack 100)
FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 in this embodiment, and FIG. 2 is an XZ diagram of the fuel cell stack 100 at a position II-II in FIG. FIG. 3 is an explanatory diagram showing a cross-sectional configuration, and FIG. 3 is an explanatory diagram showing a YZ cross-sectional configuration of the fuel cell stack 100 at a position III-III in FIG. 1 (and FIGS. 6 and 7 described later). Each figure shows mutually orthogonal XYZ axes for specifying directions. In this specification, for convenience, the positive Z-axis direction will be referred to as the upward direction, and the negative Z-axis direction will be referred to as the downward direction, but the fuel cell stack 100 is actually oriented in a different direction. may be installed. The same applies to FIG. 4 and subsequent figures.

The fuel cell stack 100 includes a plurality (seven in this embodiment) of fuel cell power generation units (hereinafter simply referred to as "power generation units") 102 and a pair of end plates 104 and 106. The seven power generation units 102 are arranged in a predetermined arrangement direction (vertical direction in this embodiment). A pair of end plates 104 and 106 are arranged so as to sandwich an assembly composed of seven power generation units 102 from above and below.

A plurality of holes (eight in this embodiment) that penetrate in the vertical direction are formed in the peripheral edge of each layer (power generation unit 102, end plates 104, 106) that constitutes the fuel cell stack 100 around the Z-axis direction. The corresponding holes formed in each layer communicate with each other in the vertical direction to form a communication hole 108 extending in the vertical direction from one end plate 104 to the other end plate 106. In the following description, the holes formed in each layer of the fuel cell stack 100 to constitute the communication holes 108 may also be referred to as the communication holes 108.

A bolt 22 extending in the vertical direction is inserted into each communication hole 108, and the fuel cell stack 100 is fastened by the bolt 22 and nuts 24 fitted on both sides of the bolt 22. As shown in FIGS. 2 and 3, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the end plate 104 that constitutes the upper end of the fuel cell stack 100, An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of the nut 22 and the lower surface of the end plate 106 that constitutes the lower end of the fuel cell stack 100. However, at a location where a gas passage member 27 (described later) is provided, an insulating sheet is placed between the nut 24 and the surface of the end plate 106, and on the upper and lower sides of the gas passage member 27 and the gas passage member 27, respectively. 26 is interposed. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass-ceramic composite, or the like.

The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each communication hole 108. Therefore, a space is ensured between the outer circumferential surface of the shaft portion of each bolt 22 and the inner circumferential surface of each communication hole 108. As shown in FIGS. 1 and 2, near the midpoint of one side (the side in the positive X-axis direction of the two sides parallel to the Y-axis) on the outer periphery of the fuel cell stack 100 around the Z-axis direction. The space formed by the located bolt 22 (bolt 22A) and the communication hole 108 into which the bolt 22A is inserted is a space into which oxidizing gas OG is introduced from outside the fuel cell stack 100, and the oxidizing gas OG is It functions as an oxidizing gas introduction manifold 161 that is a gas flow path for supplying the power generation unit 102, and inside the side opposite to this side (the side on the negative side of the X-axis of the two sides parallel to the Y-axis). The space formed by the bolt 22 (bolt 22B) located near the point and the communication hole 108 through which the bolt 22B is inserted contains oxidant off-gas OOG, which is gas discharged from the air chamber 166 of each power generation unit 102. It functions as an oxidizing gas exhaust manifold 162 that exhausts the oxidant gas to the outside of the fuel cell stack 100. Note that in this embodiment, air, for example, is used as the oxidant gas OG.

Further, as shown in FIGS. 1 and 3, the midpoint of one side (the side in the positive Y-axis direction of the two sides parallel to the X-axis) on the outer periphery of the fuel cell stack 100 around the Z-axis direction The space formed by the bolt 22 (bolt 22D) located nearby and the communication hole 108 into which the bolt 22D is inserted allows fuel gas FG to be introduced from outside the fuel cell stack 100, and the fuel gas FG to be passed through the space. A bolt that functions as a fuel gas introduction manifold 171 for supplying to the power generation unit 102 and is located near the midpoint of the side opposite to this side (the side on the negative side of the Y-axis of the two sides parallel to the X-axis) 22 (bolts 22E) and the communication holes 108 into which the bolts 22E are inserted, the space is configured to transport fuel off-gas FOG, which is gas discharged from the fuel chamber 176 of each power generation unit 102, to the outside of the fuel cell stack 100. It functions as a fuel gas exhaust manifold 172 that discharges fuel gas to. In this embodiment, a hydrogen-rich gas obtained by reforming city gas, for example, is used as the fuel gas FG.

The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body 28 and a hollow cylindrical branch 29 branching from a side surface of the main body 28 . The hole in the branch portion 29 communicates with the hole in the main body portion 28 . A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. Further, as shown in FIG. 2, the hole in the main body 28 of the gas passage member 27 located at the position of the bolt 22A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161, A hole in the main body portion 28 of the gas passage member 27 located at the position of the bolt 22B forming the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. Further, as shown in FIG. 3, the holes in the main body 28 of the gas passage member 27 disposed at the positions of the bolts 22D forming the fuel gas introduction manifold 171 communicate with the fuel gas introduction manifold 171, and A hole in the main body portion 28 of the gas passage member 27 located at the position of the bolt 22E forming the exhaust manifold 172 communicates with the fuel gas exhaust manifold 172.

(Configuration of end plates 104, 106)
The pair of end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are made of stainless steel, for example. One end plate 104 is arranged above the uppermost power generation unit 102, and the other end plate 106 is arranged below the lowermost power generation unit 102. A plurality of power generation units 102 are held in a pressed state by a pair of end plates 104 and 106. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Configuration of power generation unit 102)
FIG. 4 is an explanatory diagram showing the XZ cross-sectional structure of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 2, and FIG. FIG. 2 is an explanatory diagram showing a YZ cross-sectional configuration of two power generation units 102. FIG. In the upper part of FIG. 5, the YZ cross-sectional configuration of a portion of the power generation unit 102 is shown in an enlarged manner. 6 is an explanatory diagram showing the XY cross-sectional configuration of the power generation unit 102 at the VI-VI position in FIG. 4, and FIG. 7 is an explanatory diagram showing the XY cross-sectional configuration of the power generation unit 102 at the VII-VII position in FIG. FIG.

As shown in FIGS. 4 and 5, the power generation unit 102 includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, a fuel electrode side frame 140, and a fuel electrode side frame 130. It includes a current collector 144 and a pair of interconnectors 150 forming the uppermost layer and the lowermost layer of the power generation unit 102. Holes corresponding to the communication holes 108 into which the bolts 22 described above are inserted are formed in the peripheral edges of the separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the interconnector 150 around the Z-axis direction.

The interconnector 150 is a substantially rectangular flat plate-shaped conductive member, and is made of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents reaction gases from mixing between the power generation units 102 . In addition, in this embodiment, when two power generation units 102 are arranged adjacently, one interconnector 150 is shared by the two adjacent power generation units 102. That is, the upper interconnector 150 in a certain power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Furthermore, since the fuel cell stack 100 includes a pair of end plates 104 and 106, the uppermost power generation unit 102 in the fuel cell stack 100 does not include the upper interconnector 150, and the lowermost power generation unit 102 does not include the upper interconnector 150. The power generation unit 102 does not include a lower interconnector 150 (see FIGS. 2 and 3).

The single cell 110 includes an electrolyte layer 112, a fuel electrode (anode) 116 disposed on one side (lower side) of the electrolyte layer 112 in the vertical direction (first direction), and the other side of the electrolyte layer 112 in the vertical direction. It includes an air electrode (cathode) 114 arranged on the upper side, and an intermediate layer 180 arranged between the electrolyte layer 112 and the air electrode 114. Note that the single cell 110 of this embodiment is a fuel electrode supported type single cell in which the fuel electrode 116 supports other layers (electrolyte layer 112, air electrode 114, intermediate layer 180) that constitute the single cell 110.

The electrolyte layer 112 is a substantially rectangular plate-shaped member when viewed in the Z-axis direction, and is a dense layer. The electrolyte layer 112 is formed of a solid oxide such as YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), GDC (gadolinium-doped ceria), or perovskite-type oxide. There is. That is, the single cell 110 (power generation unit 102) of this embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

The air electrode 114 is a substantially rectangular plate-shaped member smaller than the electrolyte layer 112 when viewed in the Z-axis direction, and is a porous layer. The air electrode 114 is formed of, for example, a perovskite oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), or LNF (lanthanum nickel iron).

The fuel electrode 116 is a substantially rectangular plate-shaped member having substantially the same size as the electrolyte layer 112 when viewed in the Z-axis direction, and is a porous layer. The fuel electrode 116 is formed of, for example, a cermet made of Ni and oxide ion conductive ceramic particles (eg, YSZ).

The intermediate layer 180 is a substantially rectangular plate-shaped member, and is formed to include GDC (gadolinium-doped ceria). The intermediate layer 180 has a structure in which an element (for example, Sr) diffused from the air electrode 114 reacts with an element (for example, Zr) contained in the electrolyte layer 112 to generate a high-resistance substance (for example, SrZrO ₃ ). suppress.

The separator 120 is a frame-shaped member in which a substantially rectangular hole 121 that penetrates vertically is formed near the center, and is made of metal, for example. The surrounding portion of the hole 121 in the separator 120 faces the peripheral edge of the surface of the electrolyte layer 112 on the air electrode 114 side. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag brazing) disposed at opposing portions. The separator 120 separates an air chamber 166 facing the air electrode 114 and a fuel chamber 176 facing the fuel electrode 116, thereby preventing gas from leaking from one electrode side to the other electrode side at the periphery of the single cell 110. suppressed.

As shown in FIGS. 4 to 6, the air electrode side frame 130 is a frame-like member in which a substantially rectangular hole 131 penetrating vertically is formed near the center, and is made of, for example, an insulator such as mica. ing. The hole 131 of the air electrode side frame 130 constitutes an air chamber 166 facing the air electrode 114. The air electrode side frame 130 is in contact with the peripheral edge of the surface of the separator 120 on the side opposite to the side facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 on the side opposite to the air electrode 114. . Further, the pair of interconnectors 150 included in the power generation unit 102 are electrically insulated by the air electrode side frame 130. The air electrode side frame 130 also includes an oxidizing gas supply communication hole 132 that communicates between the oxidizing gas introduction manifold 161 and the air chamber 166, and an oxidizing gas supply communication hole 132 that communicates between the air chamber 166 and the oxidizing gas discharge manifold 162. A discharge communication hole 133 is formed.

As shown in FIGS. 4, 5, and 7, the fuel electrode side frame 140 is a frame-like member in which a substantially rectangular hole 141 penetrating vertically is formed near the center, and is made of, for example, metal. . The hole 141 of the fuel electrode side frame 140 constitutes a fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral edge of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the fuel electrode 116 . The fuel electrode side frame 140 also includes a fuel gas supply communication hole 142 that communicates between the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that communicates between the fuel chamber 176 and the fuel gas discharge manifold 172. is formed.

As shown in FIGS. 4, 5, and 7, the fuel electrode side current collector 144 is arranged within the fuel chamber 176. The fuel electrode side current collector 144 includes an interconnector facing part 146, an electrode facing part 145, and a connecting part 147 connecting the electrode facing part 145 and the interconnector facing part 146, and is made of, for example, nickel or nickel alloy. , stainless steel, etc. The electrode facing portion 145 is in contact with the surface of the fuel electrode 116 on the side opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 is in contact with the surface of the interconnector 150 on the side opposite to the fuel electrode 116. are in contact. However, as described above, since the lowest power generation unit 102 in the fuel cell stack 100 does not include the lower interconnector 150, the interconnector facing portion 146 in the power generation unit 102 is located on the lower end plate. 106 is in contact. Since the fuel electrode side current collector 144 has such a configuration, it electrically connects the fuel electrode 116 and the interconnector 150 (or the end plate 106). Note that a spacer 149 made of mica, for example, is arranged between the electrode facing part 145 and the interconnector facing part 146. Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to temperature cycles and reaction gas pressure fluctuations, and connects the fuel electrode 116 and the interconnector 150 (or end plate 106) via the fuel electrode side current collector 144. Good electrical connection is maintained.

As shown in FIGS. 4 to 6, the air electrode side current collector 134 is arranged within the air chamber 166. The air electrode side current collector 134 is composed of a plurality of substantially square columnar current collector elements, and is made of, for example, ferritic stainless steel. The air electrode side current collector 134 is formed in a convex shape that projects from the interconnector 150 in the negative Z-axis direction (the one side (the air electrode 114 side) in the Z-axis direction). The air electrode side current collector 134 is connected to the surface of the air electrode 114 on the side opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 on the side opposite to the air electrode 114 (in contact with it). ). However, as described above, since the uppermost power generation unit 102 in the fuel cell stack 100 does not include the upper interconnector 150, the air electrode side current collector 134 in the power generation unit 102 is connected to the upper end plate. 104 is in contact. Since the air electrode side current collector 134 has such a configuration, it electrically connects the air electrode 114 and the interconnector 150 (or the end plate 104).

Note that, as shown in FIGS. 4 and 5, in this embodiment, the air electrode side current collector 134 and the interconnector 150 are formed as an integral member. That is, of the integral member (hereinafter referred to as "metal member 190"), a flat plate-shaped part perpendicular to the vertical direction (Z-axis direction) functions as the interconnector 150, and air is removed from the flat plate-shaped part. A plurality of current collector elements formed to protrude toward the pole 114 function as the air electrode side current collector 134.

As shown in FIG. 5, an oxide film layer 194 containing Cr oxide (for example, Cr ₂ O ₃ (chromia)) is formed on the surface of the metal member 190. Further, as shown in FIGS. 4 and 5, the surface of the metal member 190 (more specifically, the surface of the oxide film layer 194 disposed on the surface of the metal member 190 on the opposite side from the metal member 190) is It is covered by a conductive Mn--Co coating layer 196. Note that the oxide film layer 194 corresponds to a first film layer in the claims, and the Mn-Co film layer 196 corresponds to a second film layer in the claims.

As shown in FIGS. 4 and 5, the air electrode 114 and the air electrode side current collector 134 are joined by a conductive joint 138. The junction 138 is made of, for example, an oxide having a spinel crystal structure (for example, Mn _1.5 Co _1.5 O ₄ , MnCo ₂ O ₄ , ZnCo ₂ O ₄ , ZnMn ₂ O ₄ , ZnMnCoO ₄ , CuMn ₂ O). ₄ ). The air electrode 114 and the air electrode side current collector 134 are electrically connected by the joint portion 138 . Earlier, it was explained that the air electrode side current collector 134 is connected to (in contact with) the surface of the air electrode 114, but to be more precise, there is a gap between the air electrode side current collector 134 and the air electrode 114. A joint portion 138 is interposed therebetween.

In the following description, the metal member 190 (an integral member of the interconnector 150 and the air electrode side current collector 134), the oxide film layer 194 formed on the surface of the metal member 190, and the metal member in the oxide film layer 194 will be described. The Mn--Co coating layer 196 formed on the opposite surface from the surface facing 190 is collectively referred to as interconnector composite 200. The interconnector complex 200 is electrically connected to the air electrode 114 via the joint 138 and is also electrically connected to the fuel electrode 116 via the fuel electrode side current collector 144. The configuration of interconnector complex 200 will be detailed later. Note that the interconnector complex 200 corresponds to an interconnector member in the claims.

A-2. Operation of fuel cell stack 100:
As shown in FIGS. 2 and 4, the oxidizing gas OG is supplied through a gas pipe (not shown) connected to the branch part 29 of the gas passage member 27 provided at the position of the oxidizing gas introduction manifold 161. Then, the oxidizing gas OG is supplied to the oxidizing gas introduction manifold 161 through the branch portion 29 of the gas passage member 27 and the hole of the main body 28, and is supplied to the oxidizing gas introduction manifold 161 from the oxidizing gas introduction manifold 161 to the oxidizing gas OG of each power generation unit 102. The agent gas is supplied to the air chamber 166 via the agent gas supply communication hole 132. Further, as shown in FIGS. 3 and 5, fuel gas FG is supplied via a gas pipe (not shown) connected to a branch part 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. Then, the fuel gas FG is supplied to the fuel gas introduction manifold 171 via the branch part 29 of the gas passage member 27 and the hole of the main body part 28, and is connected to the fuel gas supply communication of each power generation unit 102 from the fuel gas introduction manifold 171. The fuel chamber 176 is supplied through the hole 142 .

When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power generation is performed in the single cell 110 by an electrochemical reaction between the oxidant gas OG and the fuel gas FG. be exposed. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to the interconnector complex 200 (assembly of the metal member 190, oxide film layer 194, and Mn-Co film layer 196) via the joint 138. The fuel electrode 116 is electrically connected to the interconnector complex 200 via the fuel electrode side current collector 144. That is, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the electrical energy generated in each power generation unit 102 is extracted from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100. Note that SOFC generates power at a relatively high temperature (for example, 700°C to 1000°C), so after startup, the fuel cell stack 100 is not connected to the heater ( (not shown).

As shown in FIGS. 2 and 4, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication hole 133, and further oxidized. The fuel cell stack 100 is passed through the main body portion 28 of the gas passage member 27 provided at the position of the agent gas discharge manifold 162 and the hole in the branch portion 29, and through a gas pipe (not shown) connected to the branch portion 29. is discharged to the outside. Further, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 via the fuel gas discharge communication hole 143, as shown in FIGS. Externally through the main body 28 and branch section 29 of the gas passage member 27 provided at the exhaust manifold 172, and through a gas pipe (not shown) connected to the branch section 29, be discharged.

A-3. Detailed configuration of interconnector complex 200:
FIG. 8 is an explanatory diagram showing the detailed configuration of the interconnector complex 200 (the part where the air electrode side current collector 134 is formed) in this embodiment. FIG. 8 shows an enlarged cross-sectional configuration of the X1 section in FIG. FIG. 9 is an explanatory diagram showing the detailed configuration of the interconnector complex 200 (of which the air electrode side current collector 134 is not formed) in this embodiment. FIG. 8 shows an enlarged cross-sectional configuration of the X2 section in FIG. As described above, the interconnector complex 200 includes the metal member 190 (an integral member of the air electrode side current collector 134 and the interconnector 150), the oxide film layer 194 disposed on the surface of the metal member 190, A Mn--Co coating layer 196 is provided on the surface of the oxide coating layer 194 on the side opposite to the metal member 190.

The metal member 190 contains Fe as a main component and also contains Cr. In addition, in this specification, the main component means the component with the highest concentration. Note that in this embodiment, the metal member 190 may further contain other elements.

The oxide film layer 194 contains Cr oxide (eg, Cr ₂ O ₃ (chromia)). The Cr concentration of the oxide film layer 194 is higher than that of the metal member 190. The thickness of the oxide film layer 194 is preferably 0.5 μm or more, for example. Since the oxide film layer 194 has low oxygen permeability, it suppresses oxidation of Fe, which is more undesirable for the metal member 190. That is, the oxide film layer 194 functions as an oxidation-resistant film. On the other hand, since the oxide film layer 194 has a relatively high electrical resistance, it is not preferable for the oxide film layer 194 to grow further as the fuel cell stack 100 is used, for example.

The Mn--Co coating layer 196 has a spinel-type crystal structure and is a conductive layer containing a spinel-type oxide containing Mn and Co (for example, MnCo ₂ O ₄ ). Note that in this embodiment, the Mn--Co coating layer 196 further contains Ni. The thickness of the Mn--Co coating layer 196 is preferably, for example, 5 μm or more (more preferably 8 to 20 μm). Since the Mn-Co film layer 196 suppresses the permeation of oxygen, it can suppress the growth of the oxide film layer 194 with high electrical resistance, and as a result, the electrical resistance of the interconnector complex 200 increases (and as a result, the power generation (deterioration in performance of the unit 102) can be suppressed. Furthermore, since the Mn--Co coating layer 196 suppresses transpiration of Cr from the metal member 190, it is possible to suppress the occurrence of Cr poisoning of the electrode (for example, the air electrode 114) of the single cell 110, and as a result, Deterioration in performance of the power generation unit 102 can be suppressed.

The ratio of the Mn concentration (atm %) to the Co concentration (atm %) in the Mn--Co coating layer 196 is 1:1 to 2. The reason why the ratio between the Mn concentration and the Co concentration in the Mn--Co coating layer 196 is set to such a value is that in a configuration in which the ratio deviates from this value, metal members 190 and oxidation This is because the difference in thermal expansion coefficient with the coating layer 194 becomes large, and as a result, the Mn--Co coating layer 196 is easily peeled off (from the oxide coating layer 194).

In any cross section parallel to the Z-axis direction (for example, the cross section shown in FIG. 8 and the cross section shown in FIG. 9), a portion of the Mn--Co coating layer 196 on the Z-axis negative direction side (hereinafter referred to as "outer portion"). ) 197 is the porosity S2 of the portion (hereinafter referred to as "inner portion") 198 located between the outer portion 197 and the oxide layer 194 of the Mn--Co coating layer 196. (%) greater than. Note that the "porosity S1 (%) in the outer portion 197" means the ratio of the total area of each pore existing in the outer portion 197 to the area of the outer portion 197, and the "porosity S2 (%) in the inner portion 198" %) means the ratio of the total area of each pore present in the inner portion 198 to the area of the inner portion 198. The same applies to the term "porosity" below.

As shown in FIGS. 8 and 9, a virtual line in the Y-axis direction (direction perpendicular to the Z-axis direction) passing through the tip of the metal member 190 on the Z-axis negative direction side in the Z-axis direction of the Mn--Co coating layer 196 The porosity Sa of the portion 1961 located in the positive direction of the Z-axis relative to the straight line L (hereinafter referred to as the "first portion") is determined by the porosity Sa of the portion 1961 located in the negative direction of the Z-axis relative to the imaginary straight line L. The porosity is smaller than the porosity Sb of the located portion (hereinafter referred to as “second portion”) 1962. In this embodiment, the porosity of the Mn--Co coating layer 196 gradually decreases like a gradation from the first portion 1961 side to the second portion 1962 side.

The ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion 197 is 60 (atm %) or more. Note that the ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion 197 may be less than 60 (atm %).

A-4. Method for manufacturing interconnector complex 200:
Next, a method for manufacturing interconnector composite 200 will be described. FIG. 10 is a flowchart illustrating an example of a method for manufacturing the interconnector complex 200 in this embodiment. Further, FIGS. 11 and 12 are explanatory diagrams schematically showing an example of a method for manufacturing the interconnector complex 200 in this embodiment.

First, a metal member 190 is prepared (S110). Note that in order to clean the surface of the metal member 190, a degreasing process using acetone may be performed. Note that in this embodiment, a Ni plating layer 151 containing Ni is formed on the metal member 190 by plating (A in FIG. 11). Note that the step S110 corresponds to the first step in the claims.

Next, a Mn oxide layer 152 is formed on the Ni plating layer 151 by electrophoretic deposition (S120, B in FIG. 11). More specifically, first, electrolytic cell Ec1 is prepared. A solution Es1 containing a ketone solvent (eg, acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone) is placed in the electrolytic cell Ec1. Next, powder of Mn oxide (for example, MnO) is added to the solution Es1 in the electrolytic cell Ec1. Further, I ₂ (iodine) is added to the solution Es1 in the electrolytic cell Ec1 (for example, I ₂ is dispersed at a concentration of 0.6 g/L). As a result, keto-enol tautomerism occurs, protons (hydrogen ions) are generated, and the generated protons are adsorbed to the Mn oxide, resulting in a charged state. A metal member 190 and an electrode E1 made of, for example, C (carbon) are placed in a solution Es1, and a voltage is applied between the metal member 190 and the electrode E1 using a power source P1 (in this embodiment, , the metal member 190 becomes a negative electrode, and the electrode E1 becomes a positive electrode). As a result, by generating an electric field in the solution Es1, the Mn oxide to which protons are attached is drawn toward the Ni plating layer 151 and adheres to the Ni plating layer 151. The protons attached to the Ni plating layer 151 become H ₂ (hydrogen) by receiving electrons, and this H ₂ is desorbed from the Ni plating layer 151 , leaving Mn oxide in the Ni plating layer 151 . As a result, a porous Mn oxide layer 152 is formed. Note that the step S120 corresponds to the third step in the claims.

Next, a Co plating layer 153 containing Co is formed on the Mn oxide layer 152 by plating (plating treatment) (S130, C and D in FIG. 12). More specifically, first, as shown in FIG. 12C, a solution Es2 containing Co ions is prepared in the electrolytic cell Ec2. Next, the metal member 190 and the electrode E2 made of Co, for example, are placed in the solution Es2, and a voltage is applied between the metal member 190 and the electrode E2 using the power source P2 (in this embodiment, , the metal member 190 becomes a negative electrode, and the electrode E2 becomes a positive electrode). This generates an electric field in the solution Es2. As a result, Co ions are attracted to the Mn oxide layer 152 side and adhere to the Mn oxide layer 152 (so as to fill the pores formed in the Mn oxide layer 152). As a result, a Co plating layer 153 is formed. Note that the step S130 corresponds to the third step in the claims. In addition, in D of FIG. 12, among the parts indicated by the symbols "152, 153", the parts with dot-like hatching are compared with the Co plating layer 153 that fills the pores formed in the Mn oxide layer 152. In contrast, the diagonally hatched areas are areas where the Co plating layer 153 fills the pores formed in the Mn oxide layer 152. It is a relatively large portion (and therefore has a relatively low porosity).

Next, the metal member 190 (more precisely, the metal member 190 (more precisely, the metal on which the Ni plating layer 151, the Mn oxide layer 152, and the Co plating layer 153 have been formed) which has undergone the steps S110, S120, and S130. By firing the member 190), an oxide film layer 194 and a Mn--Co film layer 196 are formed on the metal member 190 (S140, D in FIG. 12). More specifically, heat treatment is performed at a predetermined temperature of, for example, 1000° C. or less for a predetermined time. By performing the heat treatment, Cr contained in the metal member 190 diffuses and reacts with oxygen in the atmosphere. As a result, an oxide film layer 194 containing Cr oxide (for example, Cr ₂ O ₃ (chromia)) is formed on the surface of the metal member 190 . Further, by performing the heat treatment, Co and other elements (Mn) contained in the Co plating layer 153 diffuse and react with oxygen in the atmosphere. As a result, a Mn--Co film layer 196 containing Co oxide (eg, MnCo ₂ O ₄ ) is formed on the surface of the oxide film layer 194. By the manufacturing method described above, the interconnector composite body 200 having the above-described configuration is manufactured. Note that the step S140 corresponds to the fourth step in the claims.

A-5. Effects of this embodiment:
As described above, the interconnector complex 200 in this embodiment includes a metal member 190 containing Fe and Cr, and is arranged on the Z-axis negative direction side (one side in the Z-axis direction) of the metal member 190, Comprising an oxide film layer 194 containing a Cr oxide, and an Mn--Co film layer 196 disposed on the Z-axis negative direction side of the oxide film layer 194 and containing a spinel type oxide containing Mn and Co. ing. The ratio of the Mn concentration (atm %) to the Co concentration (atm %) in the Mn--Co coating layer 196 is 1:1 to 2. In any cross section parallel to the Z-axis direction (for example, the cross section shown in FIG. 8 and the cross section shown in FIG. The porosity S1 (%) in the inner part 198 (the part located between the outer part 197 and the oxide film layer 194 of the Mn--Co film layer 196) is higher than the porosity S2 (%) in the big.

In a conventional interconnector member, for example, when a temperature change occurs around the interconnector member (particularly on the negative Z-axis side with respect to the interconnector member), a coating layer containing Mn and Co (in this embodiment) The temperature of the portion of the Mn-Co coating layer 196 (hereinafter referred to as "Mn-Co coating layer") on the negative Z-axis side changes, and as a result, the Mn-Co coating layer and the Cr oxidation layer change. Stress is generated due to the difference in thermal expansion between the Mn-Co film layer and the film layer containing the substance (corresponding to the oxide film layer 194 of this embodiment; hereinafter referred to as the "oxide film layer"), and this causes the Mn-Co film layer to separate from the oxide film layer. May peel off.

On the other hand, in the interconnector complex 200 of this embodiment, as described above, in an arbitrary cross section parallel to the Z-axis direction, the porosity S1 (%) in the outer portion 197 of the Mn--Co coating layer 196 is ( The porosity is larger than the porosity S2 (%) in the inner portion 198 (of the Mn--Co coating layer 196). Therefore, in any cross section parallel to the Z-axis direction, the presence of pores formed in the Mn-Co coating layer 196 reduces the thermal conductivity in the Mn-Co coating layer 196, and as a result, the Mn-Co coating layer 196 deformation (thermal expansion and contraction) is suppressed. Furthermore, due to the presence of pores formed in the Mn-Co coating layer 196, the deformation (thermal expansion and thermal contraction) of the Mn-Co coating layer 196 is absorbed, and thereby the deformation (thermal expansion and contraction) of the Mn-Co coating layer 196 is absorbed. and heat shrinkage) are suppressed. Therefore, according to the interconnector complex 200 of the present embodiment, the (oxide film layer) 194) can be suppressed.

Note that from the viewpoint of suppressing peeling of the Mn-Co coating layer 196 (from the oxide coating layer 194) due to stress caused by the difference in thermal expansion between the Mn-Co coating layer 196 and the oxide coating layer 194, Mn- The porosity S1 (%) in the outer portion 197 of the Co coating layer 196 is preferably 20% or more (more preferably 30% or more). Further, the difference between the porosity S1 (%) in the outer portion 197 of the Mn--Co coating layer 196 and the porosity S2 (%) in the inner portion 198 is 10% or more (more preferably 20% or more). It is preferable.

Further, in the interconnector complex 200 of this embodiment, the ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion 197 of the Mn--Co coating layer 196 is 60 (atm% ) That's it. Therefore, in the interconnector complex 200 of this embodiment, the amount of Mn present in the outer portion 197 of the Mn--Co coating layer 196 is sufficiently larger than the amount of Co (present in the outer portion 197). As a result, the thermal conductivity of the Mn--Co coating layer 196 decreases, and heat transfer by electron movement in the Mn--Co coating layer 196 decreases. Therefore, according to the interconnector complex 200 of this embodiment, heat conduction in the Mn-Co coating layer 196 is suppressed, and stress is generated due to the difference in thermal expansion between the Mn-Co coating layer 196 and the oxide coating layer 194. Peeling of the Mn--Co coating layer 196 (from the oxide coating layer 194) caused by this can be more effectively suppressed.

Furthermore, the interconnector complex 200 of the present embodiment includes an electrolyte layer 112 and an air electrode 114 and a fuel electrode 116 facing each other in the Z-axis direction with the electrolyte layer 112 in between. In a fuel cell stack 100 that includes a plurality of (seven in this embodiment) power generation units 102 that include a single cell 110 in which a chamber 166 (and a fuel chamber 176 facing the surface of the fuel electrode 116) is formed, a metal member 190 is , a plurality of air electrode side current collectors 134 protruding in the Z-axis negative direction (the above-mentioned one side in the Z-axis direction) are formed, and the plurality of air electrode side current collectors 134 are formed with an oxide film layer 194 and a Mn-Co film. It is a conductive member that is covered with a layer 196 and is electrically connected to the air electrode 114 by connecting the plurality of air electrode side current collectors 134 to the air electrode 114. The first portion 1961 of the Mn--Co coating layer 196 (in the Y-axis direction (direction perpendicular to the Z-axis direction) passing through the tip of the metal member 190 on the negative Z-axis side in the Z-axis direction of the Mn--Co coating layer 196 ) of the second portion 1962 of the Mn--Co coating layer 196 (the portion located in the negative direction of the Z-axis relative to the imaginary straight line L) It is less than the porosity Sb.

In the interconnector complex 200 of this embodiment, the porosity S1 (%) in the outer portion 197 of the Mn--Co coating layer 196 is (of the Mn--Co coating layer 196) in an arbitrary cross section parallel to the Z-axis direction. The porosity of the Mn-Co coating layer 196 (oxide film delamination (from layer 194) can be suppressed. Here, in the interconnector composite 200 of this embodiment, as described above, the porosity Sa of the first portion 1961 of the Mn--Co coating layer 196 is the same as the porosity of the second portion 1962 of the Mn--Co coating layer 196. less than the rate Sb. In the second portion 1962 (at least partially facing the air chamber 166), due to the influence of the temperature change of the gas (oxidant gas OG) passing through the air chamber 166, the (oxide layer 194) is likely to peel off. On the other hand, since the second portion 1962 connected to the air electrode 114 does not face the air chamber 166 (except for a small part), the second portion 1962 of the Mn--Co coating layer 196 (from the oxide coating layer 194) ) There is no risk of peeling. According to the interconnector complex 200 of the present embodiment, the second portion 1962 (at least partially facing the air chamber 166) of the Mn--Co coating layer 196 has a relatively high porosity Sb. The porosity Sb of the second portion 1962 connected to the air electrode 114 is relatively low while sufficiently exhibiting the effect of suppressing the peeling of the Mn--Co coating layer 196 (from the oxide coating layer 194) described above. Accordingly, current can be efficiently passed between the interconnector complex 200 (the air electrode side current collector 134 thereof) and the air electrode 114, and the power generation performance of the fuel cell stack 100 can be improved.

Further, the method for manufacturing the interconnector composite 200 of the present embodiment includes a step of preparing a metal member 190 (S110), a step of forming a Mn oxide layer on the metal member 190 by electrophoretic deposition (S120), A metal member is formed by firing the metal member 190 that has undergone the step of forming a Co-plated layer containing Co on the Mn oxide layer 152 by plating (S130), the step of S110, the step of S120, and the step of S130. 190 includes a step of forming an oxide film layer 194 and a Mn--Co film layer 196 (S140). According to the method for manufacturing the interconnector complex 200 of the present embodiment, the ratio of the Mn concentration (atm%) to the Co concentration (atm%) in the Mn--Co coating layer 196 is 1:1 to 2. , in an arbitrary cross section parallel to the Z-axis direction, the porosity S1 (%) in the outer part 197 of the Mn--Co coating layer 196 is larger than the porosity S2 (%) in the inner part 198. Composite 200 can be easily manufactured. In addition, in the method for manufacturing the interconnector complex 200 of this embodiment, after forming the Mn oxide layer 152 by electrophoretic deposition (S120), the Co plating layer 153 is formed in the gap created in the Mn oxide layer 152. (S130), the adhesion between the Mn--Co coating layer 196 and the Mn oxide layer 152 becomes good, thereby suppressing peeling of the Mn--Co coating layer 196 (from the oxide coating layer 194). .

Furthermore, in the method for manufacturing the interconnector complex 200 of this embodiment, a ketone solvent is used as the solvent for soaking the metal member 190 in the step S120. Therefore, according to the method for manufacturing the interconnector composite 200 of this embodiment, the Mn oxide layer 152 can be formed more efficiently in the step S120.

A-6. Performance evaluation:
A sample of the interconnector complex 200 was prepared, and the performance was evaluated using the sample. FIG. 13 is an explanatory diagram showing the performance evaluation results in this embodiment. Note that the "gradient of porosity" in FIG. 13 means that the porosity S1 (%) in the outer part 197 is larger than the porosity S2 (%) in the inner part 198, The term "ratio of the amount of material" means the ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion 197.

A-6-1. For each sample:
As shown in FIG. 13, four samples (samples Sp1, Sp2, and Sp3) were used in this performance evaluation.

Sample Sp1 and sample Sp2 are samples of the interconnector complex 200 of this embodiment described above. In sample Sp1, the ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion 197 is 60 atm% or more (more specifically, 70 atm%); Sp2 differs from sample Sp1 only in that the ratio is less than 60 atm% (more specifically, 50 atm%). In sample Sp1 and sample Sp2, the outer portion 197 of the Mn--Co coating layer 196 (the Mn--Co coating layer The porosity S1 (%) in the inner part 198 (the part located between the outer part 197 and the oxide film layer 194 of the Mn--Co film layer 196) It is larger than the rate S2 (%). More specifically, in this performance evaluation, as samples Sp1 and Sp2, the porosity S1 (%) in the outer portion 197 of the Mn--Co coating layer 196 is 30% or more, and the porosity S1 (%) in the outer portion 197 is 30% or more. %) and the porosity S2 (%) in the inner portion 198 of 10% or more (more specifically, 20%). More specifically, for sample Sp1 and sample Sp2, the porosity S1 in the outer portion 197 was 30%, and the porosity S2 in the inner portion 198 was 10%.

Sample Sp3 is a sample of an interconnector complex of a comparative example. In the interconnector composite of sample Sp3, the Mn--Co coating layer 196 has a uniform porosity (the difference between the porosity S1 (%) in the outer part 197 and the porosity S2 (%) in the inner part 198 is 10 %) is different from the interconnector complexes 200 of samples Sp1 and Sp2 (this embodiment). More specifically, for sample Sp3, the porosity S1 in the outer portion 197 was 20%, and the porosity S2 in the inner portion 198 was 15%. The amount of Mn in the outer portion of sample Sp3 was 60 atm% or more (more specifically, 70 atm%).

A-6-2. Evaluation method and evaluation results:
A repeated thermal cycle test was carried out 10 times at a heating rate of 100° C./hour and a cooling rate of 100° C./hour for holding each temperature at room temperature and 900° C. for 1 hour in an air atmosphere. After that, a constant current (for example, 0.5 A/cm ² ) was applied to each of the above samples (samples Sp1, Sp2, and Sp3) in an atmosphere at 900°C to measure the electrical resistance (contact resistance) (Ωcm ² ). It was measured. It was determined that the smaller the electrical resistance value in an air atmosphere at 900° C. after 10 thermal cycle tests, the higher the evaluation (peeling of the Mn--Co coating layer 196 was suppressed). Specifically, if the electrical resistance value is 2.0 Ωcm2 ^or less, it is "◎", and if the electrical resistance value is greater than 2.0 Ωcm2 and 3.0 ^{Ωcm2 or} less, it is "○", and the electrical resistance value increases. If the value was larger than 3.0 Ωcm ² , it was determined as “×”. If it was "◎" or "○", it was determined to be "pass", and if it was "x", it was determined to be "fail".

In sample Sp3, the electrical resistance value was greater than 3.0 Ωcm ² . Therefore, the evaluation for the interconnector complex of sample Sp3 was "x". Therefore, the evaluation result of the interconnector complex of sample Sp3 was determined to be "fail".

In sample Sp1, the electrical resistance value was 2.0 Ωcm ² or less. The evaluation for the interconnector complex 200 of sample Sp1 was "◎". Therefore, the evaluation result of the interconnector complex 200 of sample Sp1 was determined to be "pass".

Further, in the interconnector complex 200 of sample Sp2, the electrical resistance value was greater than 2.0 Ωcm ² and less than 3.0 Ωcm ² . Therefore, the evaluation for the interconnector complex 200 of sample Sp2 was "○". Therefore, the evaluation result of the interconnector complex 200 of sample Sp2 was determined to be "pass".

B. Variant:
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the gist thereof. For example, the following modifications are also possible.

The configurations of the single cell 110, power generation unit 102, or fuel cell stack 100 in the above embodiments are merely examples, and can be modified in various ways.

Further, in the above embodiment, the Mn oxide layer 152 is formed by electrophoretic deposition in the step S130, but other methods (for example, electrophoretic electrodeposition, electrodeposition coating, or electrophoretic deposition) may be used. The Mn oxide layer 152 may be formed by a method (EPD).

Further, in the above embodiment, a ketone solvent is used as the solvent for soaking the metal member 190 in the step S130, but other solvents (for example, a solvent containing hydrochloric acid in ethanol) may be used.

Further, in the above embodiment, the interconnector 150 and the air electrode side current collector 134 are an integral member (metal member 190), but the interconnector 150 and the air electrode side current collector 134 are separate members. You can. In that case, the present invention is also applicable to an interconnector member composed of the interconnector 150 or the air electrode side current collector 134, the oxide film layer 194, and the Mn--Co film layer 196.

Further, in the above embodiment, the air electrode side current collector 134 is in contact with the air electrode 114 via the joint 138, but the air electrode side current collector 134 is in contact with the air electrode 114 without the joint 138. It may be possible to do so.

Further, in the above embodiment, the target is a SOFC that generates electricity using the electrochemical reaction between the hydrogen contained in the fuel gas and the oxygen contained in the oxidant gas, but the present invention is directed to It is similarly applicable to an electrolytic cell unit that is a constituent unit of a solid oxide electrolytic cell (SOEC) that utilizes the present invention to generate hydrogen, and to an electrolytic cell stack that includes a plurality of electrolytic cell units. Note that the configuration of the electrolytic cell stack is publicly known as described in, for example, Japanese Patent Application Laid-Open No. 2016-81813, so it will not be described in detail here, but it is generally similar to the fuel cell stack 100 in the embodiment described above. The structure is as follows. That is, the fuel cell stack 100 in the embodiment described above may be read as an electrolytic cell stack, the power generation unit 102 may be read as an electrolytic cell unit, and the single cell 110 may be read as an electrolytic single cell. However, during operation of the electrolytic cell stack, a voltage is applied between the two electrodes such that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode), and a voltage is applied through the communication hole 108. Water vapor is supplied as a raw material gas. As a result, an electrolytic reaction of water occurs in each electrolytic cell unit, hydrogen gas is generated in the fuel chamber 176, and hydrogen is extracted to the outside of the electrolytic cell stack through the communication hole 108. Even in the electrolytic cell unit and electrolytic cell stack having such a configuration, by employing the interconnector complex 200 having the above-described configuration, an increase in initial electrical resistance due to the presence of the Cr-Mn reaction layer can be suppressed. . Therefore, according to the interconnector complex 200 of this embodiment, current can flow more efficiently.

Further, although the above embodiments have been described using solid oxide fuel cells (SOFC) as an example, the present invention can also be applied to other types of fuel cells (or electrolytic cells) such as molten carbonate fuel cells (MCFC). Applicable.

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 100: Fuel cell stack 102: Power generation unit 104: End plate 106: End plate 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 124: Joint 130: Air electrode side frame 132: Oxidant gas supply communication hole 133: Oxidant gas discharge communication hole 134: Air electrode side current collector 138: Joint 140: Fuel electrode side frame 142: Fuel gas supply Communication hole 143: Fuel gas discharge communication hole 144: Fuel electrode side current collector 149: Spacer 150: Interconnector 151: Ni plating layer 152: Mn oxide layer 153: Co plating layer 161: Oxidizing gas introduction manifold 162: Oxidation Agent gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 180: Intermediate layer 190: Metal member 194: Oxide film layer 196: Mn-Co film layer 200: Interconnector complex E1: Electrode E2: Electrode Ec1: Electrolytic cell Ec2: Electrolytic cell Es1: Solution Es2: Solution FG: Fuel gas FOG: Fuel off-gas OG: Oxidizing gas OOG: Oxidizing agent off-gas P1: Power source P2: Power source

Claims (5)

a metal member containing Fe and Cr;
a first coating layer containing Cr oxide and disposed on one side of the metal member in the first direction;
An interconnector member comprising: a second coating layer disposed on the one side of the first coating layer and containing a spinel-type oxide containing Mn and Co,
The ratio of the concentration of Mn (atm%) to the concentration of Co (atm%) in the second coating layer is 1:1 to 2,
When the part on the one side of the second coating layer is an outer part, and the part of the second coating layer located between the outer part and the first coating layer is an inner part,
In at least one cross section parallel to the first direction, the porosity S1 (%) in the outer portion is larger than the porosity S2 (%) in the inner portion.
An interconnector member characterized by: The interconnector member according to claim 1,
The ratio of the amount of Mn to the amount of the remaining elements excluding the oxygen element present in the outer portion of the second coating layer is 60 (atm%) or more;
An interconnector member characterized by: The interconnector member according to claim 1 or 2,
The interconnector member includes an electrolyte layer and an air electrode and a fuel electrode that face each other in the first direction with the electrolyte layer interposed therebetween, and the interconnector member includes an electrolyte layer and an air electrode and a fuel electrode that face each other in the first direction with the electrolyte layer interposed therebetween. In an electrochemical reaction cell stack including a plurality of electrochemical reaction units each including an electrochemical reaction single cell in which facing gas chambers are formed, a plurality of convex portions protrude in the one of the first directions on the metal member. is formed, the plurality of convex portions are covered with the first coating layer and the second coating layer, and the plurality of convex portions are connected to the specific electrode, so that the specific electrode is electrically connected to the specific electrode. is a conductive member connected to
A direction opposite to the one in the first direction is the other direction, a direction perpendicular to the first direction is a second direction, and the metal in the first direction is in the second coating layer. A first portion is a portion located on the one side of the imaginary straight line in the second direction passing through the tip of the one side of the member, and is located on the other side of the imaginary straight line, and at least a portion thereof is located in the gas chamber. When the part facing is the second part,
The porosity Sa of the first portion of the second coating layer is smaller than the porosity Sb of the second portion of the second coating layer.
An interconnector member characterized by: A method for manufacturing an interconnector member according to any one of claims 1 to 3, comprising:
a first step of preparing the metal member;
a second step of forming a Mn oxide layer on the metal member by electrophoretic deposition;
a third step of forming a Co plating layer containing Co on the Mn oxide layer by plating;
forming the first coating layer and the second coating layer on the metal member by firing the metal member that has undergone the first step, the second step, and the third step; 4 steps,
A method of manufacturing an interconnector member, characterized in that: A method for manufacturing an interconnector member according to claim 4, comprising:
In the second step, a ketone solvent is used as a solvent to soak the metal member,
A method of manufacturing an interconnector member, characterized in that:

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